1. Field of the Invention
This invention relates to an industrial robot rotation shaft apparatus in which the rotation shaft of an industrial robot is adapted to be rotated by drive means installed therein.
2. Description of the Related Art
An industrial robot is either secured to a floor surface, or wall surface or provided on a pedestal movable along a floor surface or wall surface. FIG. 2 is a perspective view illustrating an example of an articulated industrial robot having a pedestal secured to a floor surface.
In FIG. 2, numeral 1 denotes a pedestal secured to a floor surface or the like at a predetermined location. A stationary support 2 is provided on the upper surface of the pedestal 1. A rotatable support 3 rotatable through a predetermined rotational angle .theta., and is rotatably mounted on the upper part of the stationary support 2. Rotatable support 3 and stationary support 2 together constitute a vertical rotation shaft. A pivot arm 4 having working arm 5 at its upper part is mounted on the rotatable support 3 and is capable of pivoting through pivot shaft 9 at a predetermined angle W about a substantially horizontal pivot axis. A wrist portion (not shown) is provided at the distal end of the working arm 5 and is movable upwardly and downwardly in response to pivotal movement of working arm 5 through a predetermined angle U relative to the pivot shaft 4.
FIG. 3 is a detailed, sectional view of a portion of the joint between the stationary support 2 and the rotatable support 3 indicated by the letter "A" in FIG. 2. As seen in FIG. 3, the rotatable support 3 rests on the upper part of the stationary support 2 and rotates by virtue of a crossed roller bearing 6. When the rotatable support 3 is rotatively driven by a driving force from a drive unit (not shown) the rotatable support 3 turns smoothly on the upper part of the stationary support 2 by means of the crossed roller bearing 6.
Since industrial robots are used, for example, to supply a machine tool with workpieces, minute machining scraps, machining fluids and the like which scatter during machining enter through a circumferential gap G, and directly penetrate a peripheral portion between the rotatable support 3 and stationary support 2, as shown in FIG. 3. Minute particles of foreign matter clinging to the robot or drops of water also tend to penetrate through the gap G when the industrial robot is washed or when the location at which the robot is installed is cleaned. Moisture and foreign matter that have penetrated the interior of the support portion 2 impede the operation of the crossed roller bearing 6 and impair an accurate rotating operation.
Furthermore, if a large amount of water should happen to enter through the gap G, the internal mechanism of the stationary support 2 may rust, causing the rotation drive means installed therein to malfunction.